(1) Field of the Invention
The present invention relates to a processing method and the like for displaying video and graphics, and particularly to a control for switching image resolutions in a TV receiver and the like that receives an interactive program through a digital broadcasting.
(2) Description of the Related Art
In recent years, a program called an interactive program has been broadcasted as practical usage of digital technologies. When the interactive program is provided on air, an application described in Java™, HTML, etc. is usually included in the program. Then, this application superposes information on video using graphics and/or texts for creating one content. To execute the application, the application is delivered to a TV receiver either through a digital wave that distributes the program or through a different delivery route such as the Internet. This function is called as application download or upload.
Also, the application may be the one that displays an advertisement, etc., which is unrelated to the program or content, at a corner of a screen on the TV receiver. Such an application is created by a vender different from a vender who creates an application for content, and the application here is independently downloaded from the content and executed on a TV receiver.
In general, in the interactive broadcasting like this, it is preferable that the application provides information along with graphics resolution corresponding to video resolution. This is because, if graphics resolution different from the resolution for the video is used, an enlargement and reduction process needs to be executed to unify both resolution when the information is output on a display apparatus. However, when this process is executed, pixel dithering, etc. occur, which make it difficult to keep a beautiful display.
In the meantime, in compression technologies for digital video, such as an MPEG technology, there is a huge difference in a bandwidth necessary for data transfer if video resolution varies. Because of this, in the digital broadcasting, it is necessary, from a viewpoint of saving the band for data transfer, to broadcast a program with appropriate video resolution according to its program content.
Then, a combination of the video resolution and the graphics resolution becomes an issue at this point.
That is to say, if the video resolution of a channel that has been selected up to a certain point is different from the video resolution of another channel that is newly selected, a beautiful picture can not be expected unless these graphics are displayed with the graphics resolution respectively corresponding to each of the video resolution. The most preferable selection is to use the graphics resolution equivalent to the video resolution. However, depending on a TV receiver, such graphics resolution can not be used due to some reasons such as a cost. If that is the case, it is supposed to select the graphics resolution that can provide a display as beautiful as possible.
As one of conventional technologies for realizing selection of the graphics resolution, there is a HAVi specification. HAVi (http://www.havi.org/) stands for Home Audio Video Interoperability. It stipulates a specification that allows an application operated on a TV receiver controlling the graphics resolution and the video resolution. In the HAVi specification, an API is provided to control the graphics resolution in a class called HGraphicsDevice. When the application designates ideal graphics resolution to be used, it is possible to provide and use the resolution closest to it from the graphics resolution available in the TV receiver.
In the meantime, graphics display materials with resolution according to an image format are made available in advance. And, when the video resolution is changed, its image format is determined from video packets, and graphics display materials according to the image format are displayed. By doing so, the display materials with the same quality and in the same size can be consistently shown (See Japanese Laid-Open Patent application No. 2000-23061, Japanese Laid-Open Patent application No. 2002-247465, Japanese Laid-Open Patent application No. 10-124021, and Japanese Patent No. 3315557, for example).
However, in the HAVi specification, graphics resolution, which is the closest to the desired one, is simply selected from the graphics resolution available in the TV receiver. It does not take account of an ideal combination of the graphics resolution with the video resolution received currently.
Also, in the above patent documents and the like, when the video resolution is changed, it is possible to show the display material with the same quality and in the same size on the TV receiver. However, it does not consider a layout of the application display.